A teenager has been taken to hospital after overdosing on espresso. So how much is too much coffee?

In Italy seven double espressos might be considered tame. Robbie Williams would probably class it as such, he reportedly has a 36-a-day habit.

But for 17-year-old Jasmine Willis those seven cups of strong coffee were enough to make her overdose. She says she was drenched, burning up, hyperventilating and laughing and crying at the same time in front of the customers.

So with the British increasingly embracing the coffee culture, how much is too much?

The Department of Health (DoH) advises people not to drink more than five single espressos - roughly seven instant coffees - a day, although individuals vary in their sensitivity.

The highest natural caffeine content is found in filter coffee, a mug of which contains about 120mg of caffeine. Instant coffee contains roughly 75mg and espresso 107mg.

"Provided it's taken in moderation we don't need to see coffee as a threat to health, but the recommendation is enjoy in moderation," says a spokeswoman for the British Dietetic Association.

Lethal

Indulging in a few mugs too many could result in symptoms such as restlessness, nervousness, excitement, insomnia, nausea, vomiting and a flushed face. The symptoms of a serious overdose include delirium and seizures.

Among its effects on the human body, caffeine is commonly thought to increase alertness, attention and mental ability by stimulating the central nervous system.

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But too much could be lethal. Such a dose is dependent on an individual's weight and sensitivity, but for the average person is about 90 milligrams per two pints of blood, according to coffee website Cofcaf.co.uk. This is about 200 cups of instant coffee in a day for an average sized person, it says.

Death from an extreme overdose would tend to be due to ventricular fibrillation - an uncoordinated contraction of heart muscles, which could stop blood pumping.

People can also become addicted to coffee. Caffeinism is thought to occur if you have an intake of above 600mg to 750mg of caffeine per day, says the DoH. That's roughly five to six cups of ground coffee or eight to 10 cups of instant.

But coffee has also been found to have health benefits. Drinking a daily cup or three may reduce the risk of liver diseases in heavy drinkers and one study has shown it could protect against the onset of Alzheimer's. Last month a study suggested it could help protect skin from the sun.

However, its famed effect of being a "wake up" drink was questioned earlier this year by scientists from Bristol University. They found levels of alertness among those who drank coffee were almost the same as those who had drunk none.